<i>ALCURE</i> 4431 Polymeric Isocyanate Curative Hexion Specialty Chemicals North America Central and Eastern Europe Polyurethane (PU) - Isocyanates >> MDI, diphenylmethane diisocyanate Coatings Powder coating Alcure 4431 is a polymeric, aliphatic, isocyanate curative based on H12MDI and blocked with e-caprolactam. Provides increased yellowing resistance at high temperatures and increased UV resistance. Polymeric, aliphatic, isocyanate curative based on H12MDI and blocked with e-caprolactam. Used as curing agent and in powder coatings. Provides increased yellowing resistance at high temperatures and increased UV resistance.